1. Field of the Invention
The invention relates to a thin film magnetic head for use in a magnetic recording apparatus or the like such as a hard disk drive, and a method of manufacturing the same.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in an areal recording density of a hard disk or the like. A composite thin film magnetic head, which has a laminated structure comprising a reproducing head having a magnetoresistive element (hereinafter referred to as an MR element) and a recording head having an inductive magnetic transducer, is widely used as the thin film magnetic head. The MR element has a single-layer or multilayer magnetoresistive film (hereinafter referred to as an MR film) which is sensitive to a signal magnetic field so as to exhibit a resistance change, and thus the MR film is adapted to read out information according to the resistance change of the MR film. As MR films, known are an AMR film exhibiting an anisotropic magnetoresistive effect (an AMR effect) and a GMR film exhibiting a giant magnetoresistive effect (a GMR effect).
The thin film magnetic head is formed on a block-shaped slider for moving along a recording surface of a magnetic medium, so as to be directly faced with the magnetic medium. A facing surface (hereinafter referred to as an air bearing surface) to be faced with the magnetic medium is obtained by polishing the thin film magnetic head together with the slider.
In general, many data elements (each of which is an area corresponding to 1 bit of information) are arranged on a track line formed on the magnetic medium, and a distance between the data elements is very short. Thus, when reading information of one data element, the MR film of the thin film magnetic head has to avoid being affected by magnetic fields of other data elements adjacent to the data element. Therefore, the thin film magnetic head has a structure such that the MR film is sandwiched in between a pair of shield layers having high magnetic permeability. A distance between the shield layers substantially corresponds to the distance between the data elements.
In accordance with a recent increase in the areal recording density of the hard disk or the like, it is required that the distance between the shield layers of the thin film magnetic head be further reduced in order to increase an arrangement density (i.e., a linear density) of the data elements on the track line. It is required that the distance between the shield layers be reduced to 80 nm or less in order to achieve the areal recording density in excess of 30 Gbit/inch2 (4.7 Gbit/cm2), for example.
However, such a reduction in the distance between the shield layers may cause the shield layers to deform and thus come into contact with the MR film, when the slider and the thin film magnetic head are polished to form the air bearing surface. In this case, a problem exists: that is, a short circuit occurs between each shield layer and the MR film, and thus, during the reading of information, a part of a sense current to pass through the MR film passes through the shield layers, so that this leads to an output decrease.
In order to prevent such a contact of the shield layers with the MR film, it is possible that the shield layers are made of a deformation-resistant material, namely, a material having high hardness. For example, in Unexamined Japanese Patent Application Publication No. Hei 2-116009, it is proposed that a shield layer is made of FeAlSi (sendust). Moreover, in Unexamined Japanese Patent Application Publication No. Sho 60-239911, it is proposed that a shield layer is made of an amorphous magnetic alloy. Furthermore, in Unexamined Japanese Patent Application Publication No. Hei 6-195643, it is proposed that a shield layer is made of an alloy made of Fe, N (nitrogen) and M (Ta (tantalum), Hf (hafnium) or the like).
However, the following problems in manufacturing exist when the shield layers are made of the material having high hardness as mentioned above. That is, one problem is as follows. Generally, the shield layers are formed by means of sputtering and are then patterned by use of ion milling or the like, and thus, when the shield layers are made of the above-mentioned material having high hardness, patterning requires long-time ion milling, which leads to deterioration in productivity. Another problem is as follows: that is, any of the above-mentioned materials having high hardness has low thermal conductivity and thus cannot efficiently diffuse heat generated by the MR film, so that this leads to a rise in temperature of the MR film.